The Swiss Re Tower, more commonly known as the Gherkin, is reportedly up for sale for at least £600m, making it the most expensive office block ever to come onto the market. The distinctive London building at 30 St Mary's Axe has 34 office floors, of which 16 are occupied by owners Swiss Re and the remainder by other firms including Coutts, Allianz and law firm Kirkland, Ellis and Mayer. The building fetches £27m per year in rent when all office space is occupied, which would give a yield of below 4.5% if the asking price was achieved.